After the operators had spoken with us, they decided in 2008 to test the efficiency of a HUBER RakeMax® screen with 10 mm bar spacing in one of the channels. As the results of the test phase were very positive, the customer kept the screen and ordered the same type of screen also for the two other channels. The new screens do not need an additional upstream coarse screening. There was enough space then in the inlet channel in the screen building to install an about 3.5 ton new power screen for practical tests. Besides, the wastewater volumes on WWTP Hetlingen are big enough to objectively assess screen performance.
Different types of trash and especially big pieces will be thrown into the channel during the tests, such as wood pallets, car tyres, big pieces of wood, etc., to test that even these are reliably removed from the wastewater flow. ‘Fortunately, no-one here throws car tyres or similar things into a sewer. I saw a bicycle tyre once but that was an absolute exception. Besides, the disposal of such material to sewer system is illegal anyway here”, says Lutz Altenwerth, managing director of AZV Südholstein. ‘But in this case it is for a good purpose. Finally, if things work out well, the new screen will perhaps help to protect the environment somewhere else in the world.’